1. Field of the Invention
The present invention relates to a projection lens provided in the projector apparatuses and the like. In particular, the invention relates to a fixed focus projection lens and a projection-type display apparatus suitable for projecting an original image, which is formed by rays optically modulated by a light valve such as a liquid crystal display device or a micro mirror device, onto a screen in an enlarged manner.
2. Description of the Related Art
So-called front projection-type projector apparatuses for projecting an image on a screen in front of the apparatuses have come into widespread use for various applications such as school education, training in corporations, and presentations.
As projections lenses provided in such projector apparatuses, there are projection lenses centered on functions for improvement in optical performance, an increase in angle of view, an increase in magnification, and the like, and on the other hand there are more compact and lower-cost projection lenses.
In order to achieve compactness and low cost, generally fixed focus lenses, in which the zoom function is removed, are used, or the number of lenses is reduced. For example, the later-described JP-A-09-318876 and JP-A-2001-124988 proposed fixed focus projection lenses each of which has five lens elements.